The present invention relates to a self-piercing nut holding device for use in association with an automatic assembling machine by which the nuts are successively affixed to a metal panel.
The self-piercing nut, commonly so called, is known in the art, and widely used, particularly in the automobile and the electric appliance industries. As its name implies, this nut has an end face serving as a punch against a metal panel, thereby causing the nut to punch an installation aperture in the metal panel placed on a swaging die by pressure exerted on the nut.
To carry out a smooth automatic assembling operating, it is essential to feed a succession of self-piercing nuts (hereinafter referred to merely as nuts) smoothly. In addition, each nut must take a right posture at the punching position; otherwise the nut would fail to be affixed to the metal panel or would be affixed in a wrong posture thereto. Here is a difficulty in holding the succession of nuts in the right or "ready" posture with respect to the metal panel. This requires a delicate handling touch upon the individual nuts delivered at the punching position. The inventor invented a holding device which incorporated such requirements. The invention is disclosed in Japanese Utility Model Publication No. 52-31488.
According to the prior invention, the holding device has a pair of elastic members fitted in depressions produced in opposite walls of the device, wherein the elastic members are intended to hold the nut placed at the punching position "softly". This had yielded a desirable result, and dispelled a worry about a possible mallocation of the nut on the metal panel due to its inadequate posture. In addition, the provision of the elastic member had eliminated the necessity of providing an intricate device specially built for holding the nuts in an orderly manner. As a result, the holding device was extremely simplified in construction, which reflects in the production cost. The simplified construction leads to a minimized size of the assembling machine in which the nut holding device is essentially required. This will be of particular advantage when the assembling machine is united with a press unit, which has a limited accommodation space.
Through the repeated use, however, one drawback has been discovered in the life of the elastic members. This is fatal to the automatic assembling operation.